Fix %%COERCE-FIXNUM-TO-SINGLE-FLOAT for negative fixnums.
Fix %%COERCE-FIXNUM-TO-SINGLE-FLOAT for negative fixnums.

froggey/Mezzano,varjagg/Mezzano,rvedam/Mezzano,varjagg/Mezzano,froggey/Mezzano,rvedam/Mezzano